The current width of the header-left block is not enough to display logo + slogan on your site. You can access Backend > Extensions > Templates > select JA Simpli style > Layout configuration and change the block width: http://prntscr.com/cgye3z (you can change to 7 for example)
Then open the ‘custom.css’ file where you add your custom change in css and remove the margin-left property:
.navbar-brand .slogan {
display: inline-block;
text-align:top;
/* margin-left: 150px; */
font-size: 24px;
text-transform:none;
}
Now, the slogan will stand next to the logo, if you want they are closer, you can reduce the width of the logo a bit:
a.logo strong {
width: 200px;
height: 100px;
}
Hope this helps.